Life On Mars: Swimming Right Under the Surface?

As NASA struggles to refocus its Mars program on the heels of two failed missions, one supremely logical mantra has emerged to guide the search for Martian life: Follow the water. Great advice. But hard to heed on such a dry and dusty planet. No matter how much water might once have flowed on Mars, the place now looks downright dead. Liquid water, if it exists, might be a mile deep or more, scientists say. But there are two places where water is known to exist in mass quantities, right at the surface: The polar caps.